Coal production is relatively slow to ramp up/down. Some are better than others.But its production is
Meanwhile renewables can be curtailed or brought back online pretty darn quickly (that's the thing with having more renewable capacity than is needed at any time - something you can do when it's so bloody cheap and fast to build), while batteries are responding within milliseconds with their FCAS activity. Gas peaker plants have lost a significant amount of earnings to batteries and can no longer extract exorbitant fees for rapid response any more. The batteries are doing it better, faster, more reliably and for much lower cost.
And grid management isn't just about supply, there is smart demand management as well. e.g. in NSW the Tomago aluminium smelter (which currently draws ~ 850MW) is moving away from steady state coal supply to entirely renewable electricity supply as they rework their plant to produce based on when the energy is available. No longer will it be "baseload demand". That alone is one massive customer at 10-15% of the state's total electricity demand.
South Australia's grid is now at 61% renewables over a full year. There is zero hydro and zero coal. Battery discharging (including Hornsdale) only represented 0.6% of grid supply. Yes they have their contingency gas (and the odd diesel) plants in place if/when needed but it's affordable because the cost of renewables is so good now. Natural gas is their fill in fuel but it's contribution to their grid is dropping like a stone. Amazingly the amount of firming storage capacity required to get to 60% renewables has been bugger all. Their only real reliability problem was caused when major transmission infrastructure got taken out by storms. Much more storage is coming as gas's contribution will continue to decline.